Question

A man standing on a platform finds that a train takes 3 seconds to pass him and another train of the same length moving in the opposite direction, takes 4 seconds. The time taken by the trains to pass each other will be :

• A. 17/7 seconds
• B. 24/7 seconds
• C. 31/7 seconds
• D. 38/7 seconds

Answer 1

The correct option is B 24/7 seconds

Let the length of the first train=l meter

Let the length of the second train =l meter

$\therefore$Speed of the first train$=\frac{l}{3}m/sec$

$\therefore$Speed of the second train$=\frac{l}{4}m/sec$

Since both train are moving in opposite direction

$\therefore$Relative Speed$=(\frac{l}{3}+\frac{l}{4})$

$=\frac{7l}{12}m/sec$

Time taken to pass each other$=\frac{distancetobecovered}{Relativespeed}$

$=\frac{l+l}{\frac{7l}{12}}$

$=\frac{2l+12}{7l}=\frac{24}{7}sec$